Process for identifying objects using an optical spectrometer and a transport system

ABSTRACT

The invention relates to a process and an apparatus for identifying articles which are at least partly made from at least one polymer, using an optical spectrometer and a transport system, said process comprising the steps of:  
     a) moving the articles past the optical spectrometer using the transport system  
     b) irradiating the articles and measuring the response of the irradiated articles using the optical spectrometer, analyzing the response to identify the articles as to the type of polymer wherein the process also comprises the step of  
     c) at least periodically irradiating an external reference object, measuring the response of the irradiated reference object using the optical spectrometer, and using the measured response for the analysis of step b).

[0001] The invention relates to a process for identifying articles whichare at least partly made from at least one polymer, using an opticalspectrometer and a transport system, said process comprising the stepsof:

[0002] a) moving the articles past the optical spectrometer using thetransport system

[0003] b) irradiating the articles and measuring the response of theirradiated articles using the optical spectrometer, analyzing theresponse to identify the articles as to the type of polymer.

[0004] Such a process is known from WO-A-9725605.

[0005] In the process described in WO-A-9725605 the articles areidentified using infrared spectroscopy, while the articles are movedpast the infrared spectrometer, for instance using a continuously drivenbelt. The articles are irradiated, and recognized based on theinformation included in the spectrum which the articles reflect. Thearticles may then be transported to a location in accordance with theidentification.

[0006] In particular if the spectra of the different types of polymersare only slightly different, which is for instance the case fordifferent types of polyamides, such as for instance polyamide-6 andpolyamide-6,6, small variations in the measuring conditions can make thedistinction between such polymers difficult. In particular if atransport system is used to move the articles past the opticalspectrometer, it is difficult to prevent variations in the measuringconditions. A cause of such variations is for instance a fluctuation intemperature, a fluctuation in humidity and the generation of dust duringtransport, in particular in a large-scale process. A lot of dust may inparticular be generated if the articles are waste articles or usedarticles. Other variations in measuring conditions include for instancevariations in the intensity of the light source and variations in thedetector.

[0007] It is an object of the invention to provide a process in whicharticles having a polymer surface, can be effectively identified as tothe type of polymer, using a transport system.

[0008] This object is achieved according to the invention by providing aprocess for identifying articles which are at least partly made from atleast one polymer, using an optical spectrometer and a transport system,said process comprising the steps of:

[0009] a) moving the articles past the optical spectrometer using thetransport system

[0010] b) irradiating the articles and measuring the response of theirradiated articles using the optical spectrometer, analyzing theresponse to identify the articles as to the type of polymercharacterized in that the process also comprises the step of

[0011] c) at least periodically irradiating an external referenceobject, measuring the response of the irradiated reference object usingthe optical spectrometer, and using the measured response for theanalysis of step b).

[0012] According to the invention an effective identification isachieved, even if the polymers exhibit only a slightly differentresponse, such as for instance polyamid-6 and polyamid-6,6. According tothe invention, the articles can be transported at high speed past theoptical spectrometer, while keeping the fraction of correctly identifiedarticles high.

[0013] It is noted that U.S. Pat. No. 5,952,660 describes a hand-heldinfrared spectrometer for discriminating between polyamide-6 andpolyamide-6,6. In this publication it is described that a referencemeasurement is performed. For the hand-held infrared spectrometer builtin accordance with U.S. Pat. No. 5,952,660, an internal reference objectis used, i.e. a reference object which is inside the housing of thespectrometer.

[0014] As an external reference object may be used any reference objectwhich is placed outside the optical spectrometer. An opticalspectrometer generally comprises a light source for irradiating thearticles to be identified, a detector for measuring the response of theirradiated articles and a wave length selector. The spectrometer mayalso comprise a housing in which the light source and the detector, andoptionally, the wave length selector are present. If the spectrometercomprises a housing in which the light source and the detector arepresent, any reference object which is placed outside the housing may beused as an external reference object. If the spectrometer does notcomprise a housing in which the light source and the detector arepresent, any reference object may be used as an external referenceobject.

[0015] Preferably a reference object is used having a surface of a knownmaterial and/or of a material having surface properties which do notsubstantially change over time. Examples of suitable reference materialshaving surface properties which do not substantially change over timeinclude ceramic materials, metals which do not substantially oxidize inthe atmosphere, such as for instance, copper, brass, metals having aprotective oxide layer, such as for instance stainless steel oraluminum. Polymer reference materials having surface properties which donot substantially change over time may also be used, such as forinstance Teflon or polystyrene. Preferably, the surface properties ofthe reference object are such that diffuse reflection is achieved uponirradiation. This improves the accuracy of the measurement. Such surfaceproperties may for instance be achieved by roughening the surface, forinstance by grinding and/or sand blasting.

[0016] The measured response of the irradiated reference object is usedfor the analysis of step b), i.e. for the analysis of the response ofthe irradiated articles to identify the articles as to the type ofpolymer. In a preferred embodiment, the response of the irradiatedreference object is used for correction of background signals. In thisembodiment the measured response of the reference object may be used forthe calculation of the absorption according to formula 1.

A _(λ) =−log(I_(λ(article)) /I _(λ(reference material)))  (1)

[0017] where A_(λ) is the absorption at wavelength λ and I_(λ) is thelight intensity of the reflected light at wavelength λ. The calculatedabsorption may then be further analyzed to identify the articles as tothe type of polymer. For said analysis the data are preferably subjectedto a pre-treatment, such as for instance smoothing, taking a derivativeor normalization. Said pre-treated data may subsequently be subjected toclassification and/or qualification. Methods known in the art, such asfor instance a principle component analysis, partial least squareanalysis, or multi-linear regression may advantageously be used.Suitable techniques are described in “Multivariate Calibration”, byHarald Martens and Tormod Naes, John Wiley & Sons (1991) Great Brittain.The calculated values for the absorption are preferably processed, andthe processed data may be compared with known data for known types ofpolymer. For instance, in a principle component analysis, known data forknown polymers may be used to define a box in a two-dimensional plot.The processed data of the articles to be identified may be plotted inthe same two-dimensional plot. If the processed data of the articlesfall within a box corresponding to a known type of polymer, the articleto be identified is recognized as the type of polymer corresponding tosaid box.

[0018] In another preferred embodiment, the response of the irradiatedreference object is used for correction for drift. This embodimentfurther improves the accuracy of the identification. In this embodiment,the reference object has preferably a surface made from a known polymer,said known polymer being one of the polymers to be identified. By atleast periodically irradiating and measuring the response of saidsurface, the drift, i.e. the change of the response over time for apolymer, may be determined. Said change may then be used to change theknown data for said polymer, for instance by shifting the position ofthe abovementioned box in the two-dimensional plot.

[0019] It is to be understood that more than one reference object may beat least periodically irradiated. It is for instance possible, that theresponse of a reference object, preferably having surface propertieswhich do not substantially change over time, is used for correction ofbackground signals, and that one or more other reference objects,preferably having a surface of one or more of the polymers to beidentified, is used for the correction of drift. It is possible thatmore than one reference objects are combined to form one structurehaving surfaces of different reference materials.

[0020] At least periodically an external reference object is irradiated,and the response of the irradiated reference object is measured usingthe optical spectrometer. With “At least periodically” is meant atintervals or continuously. Usually the irradiation of the externalreference object, and the measuring of the response of the irradiatedobject is performed at intervals. It is possible that the intervals areequal to each other, but this is not necessary. The preferred intervalsbetween the reference measurements may depend on the extent to whichvariations in the measurement conditions occur and on the extent towhich the responses of the irradiated articles are similar. If thevariations in the measurement conditions vary to a high extent, it isdesirable that the intervals between the reference measurements isrelatively short. If the spectra of the polymers to be distinguished areonly slightly different, it also desirable that the intervals betweenthe reference measurements are relatively short. The reference objectmay advantageously be moved past the optical spectrometer using endlesstransport means, such as for instance an endless transport rail or anendless belt. The reference measurement may then be performed every timethat the reference object is moved past the optical spectrometer. Mostpreferably the reference object is moved past the optical spectrometerusing the transport system. This allows the reference measurement, i.ethe irradiation of the reference object and the measurement of theresponse, to be carried out in an effective way without interrupting thetransport of the articles.

[0021] Preferably, the reference object is moved past the opticalspectrometer while it is irradiated. This is in particular advantageouswhen the articles to be identified are also moved past the opticalspectrometer while they are irradiated. This allows the reference objectto be irradiated in a way comparable to that of articles to beidentified, which improves the accuracy.

[0022] In a preferred embodiment, the reference object is fixed to thetransport system and the fixed reference object is moved past theoptical spectrometer and irradiated. This allows the reference object tobe moved past the spectrometer in a predetermined position, whichimproves the accuracy of the measurement. A predetermined position ofthe reference object may for instance be a predetermined distance to thespectrometer during irradiation and/or a predetermined angle with theirradiation beam during irradiation. Fixing the reference object to thetransport system may for instance be carried out by fixing the referenceobject to a movable belt of a conveyor or to means, for instance acarriage, which are movable along a transport rail.

[0023] In a particularly preferred embodiment the reference object andthe articles are fixed to the transport system, and the fixed referenceobject and fixed articles are moved past the optical spectrometer, andirradiated. Fixing the reference object and the articles to thetransport system allows the reference object and the articles to bemoved past the spectrometer in a predetermined position, which improvesthe accuracy of the identification. A predetermined position of thearticles may be for instance a predetermined distance to thespectrometer during irradiation and/or a predetermined angle with theirradiation beam during irradiation. It will be understood that thepredetermined position of the articles and the predetermined position ofthe reference materials are not necessarily the same. However, it isadvantageous if the predetermined distance from the reference object tothe spectrometer during irradiation and the predetermined distance fromthe articles to the spectrometer during irradiation is approximately thesame. Fixing the articles to the transport system may for instance becarried out by fixing the articles to a movable belt of a conveyor or tomeans, for instance a carriage, which is movable along a transport rail.Preferably, the transport system comprises a transport rail and thereference object and articles are fixed to the transport rail, and thefixed reference object and fixed articles are moved past the opticalspectrometer, and irradiated. This embodiment allows a very accurateidentification of the articles. This embodiment is in particularlyadvantageous if the articles are textile materials, such as for instancecarpets and/or carpet materials.

[0024] In a preferred embodiment, separate detecting means are used fordetecting when a reference object is in front of the opticalspectrometer. This is a simple and effective way for recognizing that areference object is in front of the spectrometer. Separate detectingmeans are understood to be any suitable means for detecting the presenceof a reference object, apart from the spectrometer itself. A lightsensor or a mechanical sensor may advantageously be used.

[0025] In a preferred embodiment, a predetermined surface the articlesand/or reference object is irradiated and the process also comprises thestep d) of determining when the predetermined surface of the articlesand/or reference objects is in front of the spectrometer, and startingthe irradiation, measuring and/or analyzing the response, for eacharticle and/or reference object individually, while the predeterminedsurface of said individual article and/or reference object is in frontof the spectrometer. The predetermined surface is preferably a surfacewhich is in a predetermined position, for instance having apredetermined angle with the irradiation beam or having a predetermineddistance to the spectrometer, when irradiated by the irradiation beam.Preferably, the irradiation, measuring the response, and/or analyzingthe response is stopped while the predetermined surface of saidindividual article and/or reference object is in front of thespectrometer. This embodiment is in particular advantageous when apredetermined surface of flexible articles, for instance textilearticle, in particular carpets, is irradiated. Such predeterminedsurface may be a part of an article which can be irradiated through anopening in a clamp, said clamp fixing the article to the transportsystem. As used herein “in front of the spectrometer” denotes that thepredetermined surface can be reached by the irradiation beam orirradiation beams of the optical spectrometer. As used hereing “startingthe analyzing of the response while the predetermined surface is infront of the optical spectrometer” denotes analyzing a set of data whichhave been measured during a time interval, the start of said timeinterval being within a period within which the predetermined surface isin front of the optical spectrometer. It is possible that separatedetecting means are used for detecting when a the predetermined surfaceis in front of the optical spectrometer. This is a simple and effectiveway for recognizing that the predetermined surface is in front of thespectrometer. Separate detecting means are understood to be any suitablemeans for detecting the presence of an article, apart from the opticalspectrometer. A light sensor or a mechanical sensor may advantageouslybe used.

[0026] The invention is not limited to a specific type of opticalspectrometer. A Raman spectrometer may for instance be used. Preferably,the optical spectrometer is an infrared spectrometer. As used hereininfrared spectrometers also include mid-infrared spectrometers andnear-infrared spectrometers. A very suitable spectrometer has beendescribed in WO-A-9725605, the contents of which are herewithincorporated by reference. A near-infrared spectrometer is very suitablefor distinguishing between polyamide-6 and polyamide 6,6.

[0027] The process according to the invention is in particular suitable,if at least part of the articles are at least partly made from apolyamide, for instance polyamide-6 and/or polyamide 6,6. The processaccording to the invention is very well suitable to distinguish betweenpolymers of which the spectral response following irradiation is onlyslightly different, such as for instance polyamide-6 and polyamide-6,6.If it is to be distinguished between polyamide-6 and polyamide-6,6, PETand polypropylene, which are typical materials for face fibres ofcarpets, it is advantageous to use spectral information in the range of1000 to 3000 nm, preferably 2000 to 2600 nm.

[0028] The process according to the invention is very suitable if thearticles are textile articles, more in particular carpet or carpetmaterials, most in particular waste textile articles, carpets or carpetmaterials.

[0029] The transport system is not limited to a specific kind oftransport system. A conveyer may for instance be used. Preferably, atransport system is used which comprises a transport rail, to which thearticles can be movably connected. A suitable transport system of thistype has been described in WO-A-9906160, the contents of which areherewith incorporated by reference.

[0030] The invention also relates to an apparatus for identifyingarticles, in particular textile materials and/or carpets, said apparatuscomprising:

[0031] a) an optical spectrometer (1)

[0032] b) a transport system, said transport system comprising atransport rail (2) and transport units (3), the transport unitscomprising a body (4), coupling means (5) for fixing the articles (6) tothe transport units, the transport units being movably connected to thetransport rail

[0033] c) a guide system (8,9) which is capable of cooperating with thebody and/or coupling means, said guide system at least being present inthe area of the optical spectrometer.

[0034] When this apparatus is used, the accuracy of the identificationis improved.

[0035] In a preferred embodiment the guide system comprises a guidingelement which is essentially parallel to the transport rail, saidguiding element being capable of cooperating with the body and/orcoupling means. The guiding element may for instance be a guide rail.Preferably, the body and/or coupling means comprise one or more guidingmembers which can cooperate with the guiding element. More preferably,the body and/or coupling means comprise at least two guiding memberswhich can cooperate with the guiding element. Preferably, the guidingmembers are rotatable elements, such as for instance wheels.

[0036] In a preferred embodiment the guide system comprises a pair ofguiding elements which are essentially parallel to the transport railand which are capable of receiving the body and/or coupling means. Thepair of guiding elements may for instance be a pair of guide rails.

[0037] In a preferred embodiment, the guide system is a transversalguide system. A transversal guide system includes any system which iscapable of preventing movement of the body and/or coupling means in thetransversal direction, in particular in the direction of the irradiationbeam or irradiation beams of the optical spectrometer.

[0038] In another preferred embodiment, the guide system is alongitudinal guide system. A longitudinal guide system includes anysystem which is capable of preventing movement of the body and/orcoupling means around the transversal direction, in particular around anaxis parallel to the irradiation beam or the irradiation beams of theoptical spectrometer.

[0039] Most preferably, the guide system includes a transversal guidesystem and a longitudinal guide system.

[0040] Preferably, the coupling means have openings through which anarticle which is coupled with said coupling means can be irradiated withan irradiation beam.

[0041] In a preferred embodiment the coupling means are up and downwardmovable, the body is provided with a pulley for the up and downwardmovement of the coupling means, the pulley is movable by a frictionelement and a contact rail is present in the area of the opticalspectrometer which can cooperate with the friction element.

[0042] As a carriage may be used any means which can be movably fixed tothe transport rail. The body forms the connection between the carriageand the coupling means.

BRIEF DESCRIPTION OF THE DRAWINGS

[0043]FIG. 1 shows a schematic view of a preferred embodiment of theprocess according to the invention.

[0044]FIG. 2 shows a schematic top view of a preferred embodiment forirradiating an article.

[0045]FIG. 3 shows a schematic view of a preferred embodiment in which aguide system is present.

DETAILED DESCRIPTION OF A PREFERRED EMBODIMENT

[0046] A preferred embodiment of the invention is described withreference to FIG. 1. Articles to be identified, in this case carpets (6)or pieces of carpet, fixed to transport rail (2) via transport units (3)and clamps (5), are moved past two near-infrared (NIR) spectrometers (1)in the direction as indicated by the arrow, for instance at a rate of1000 m/s. Transport rail (2) is an endless rail which forms a loop (notshown). Fixing the carpets carpets (6) to transport rail (2) takes placebefore they are moved past NIR-spectrometers (1). During movement of thecarpets (6) past NIR-spectrometers (1) a part of the surface area ofcarpets (6) is irradiated by irradiation beams (20) of NIR-spectrometers(1). Carpets (6) are irradiated via an opening (11) in clamps (5). Theirradiated parts of the carpets are in a transverse position duringirradiation. Diffuse reflectance is measured using a detector (notshown) in NIR-spectrometers (1). For instance a spectrum covering therange from 2400 to 2510 nm may be measured if it is to be distinguishedbetween polyamide-6, polyamide-6,6, PET, and polypropylene. The measuredreflection is analyzed, for which analysis the absorption is calculatedusing the results of a prior performed reference measurement. Theresults are further analyzed, for instance by using a principlecomponent analysis, to identify the carpets as to the type of polymer,in this case the type of polymer of the face fibre of the carpets. Forthis analysis a correction is made for drift using the results of aprior performed reference measurement. Following irradiation the carpetis moved further and released at a location in accordance with itsidentification. Following the release of the carpets other pieces ofcarpet to be identified is fixed to the clamps (5).

[0047] Reference object (30) is also fixed to transport rail (2), andmoved past NIR-spectrometers (1). In this case reference object (30) isa roughened stainless steel plate. The angle of the stainless steelplate with irradiation beam (5) may be adjustable, but this angle isgenerally kept constant during the course of the process. A secondreference object (33), in this case a piece of carpet made from a knownpolymer, e.g. polyamide-6, and a third reference object, in this case apiece of carpet made from a known polymer, e.g. polyamide-6,6 (notshown), are also fixed to transport rail (2), and moved pastNIR-spectrometers (1). If the reference object (30) has come in front ofirradiation beams (20), its presence is detected using sensor (32) whichdetects radiation which is reflected by reflecting patch (31) uponirradiation by the sensor. Following detection of the reference objectby the sensor, reference object (30) is irradiated using irradiationbeams (20) while being moved past NIR-spectrometers (1). The diffusereflectance of reference object (30) is detected in the same wave lengthrange as that of the carpets. The measured reflectance from thereference object (30) is used for the calculation of the absorption ofthe carpets which are subsequently irradiated, until the referenceobject is irradiated again. During movement of the second (33) and thirdreference objects past NIR-spectrometers (1) a part of the surface areaof reference objects is irradiated by irradiation beams (20) ofNIR-spectrometers (1) in the same way as for the carpets to beidentified. The measured response from second reference object (33) andthird reference object (not shown) is used for the correction of drift.All reference objects remain fixed to the transport rail throughout theprocess, so that a reference measurement may be performed any time thata reference object is moved past NIR-spectrometers (1). Transport rail(2) may for instance be provided with 50 transport units (3) and withthree reference objects (30, 33 and a third one), in which case threereference measurements are performed per 50 carpets.

[0048] Description of a Preferred Embodiment for Irradiating an Article

[0049] Below, a preferred embodiment is described for irradiating anarticle with reference to FIGS. 1 and 2. Articles, in this case carpets(6) are fixed to transport rail (2) via transport units (3) comprising abody (4) and clamps (5), the transport units being movable alongtransport rail (2). Clamps (5) are provided with openings (11) throughwhich a part of the surface of the carpets (the predetermined surface, 6a) can be irradiated with irradiation beams (20) of near-infrared (NIR)spectrometers (1). Transport units (3) are constructed in such a waythat rotation around a vertical axis is prevented during movement pastNIR-spectrometers (1). During movement past NIR-spectrometers (1) thepredetermined part (6 a) of carpets (6) in openings (11) are in apredetermined transverse position. Each transport unit (3) is providedwith reflecting patch (21) which is detectable by sensor 22 (which iscapable of detecting the reflection of sensor irradiation beam (23)which is continuously emitted) at a moment at which the predeterminedsurface is in front of the irradiation beams (20), which arecontinuously emitting during the process. At the moment that reflectingpatch (21) is detected by sensor (22) measuring of the response of theirradiated predetermined surface is started. The measuring of theresponse is terminated before the predetermined surface has ceased to bein front of the NIR-spectrometers (1). It will be appreciated that it isalso possible that reflecting patch (21) has such a position that it isdetectable by sensor (22) at a moment before the predetermined surfaceis in front of the irradiation beams (20) and that the moment at whichthe predetermined surface becomes in front of the irradiation beams (20)is derived from the rate at which transport takes place. It will beappreciated that it is also possible that irradiation, measuring theresponse and analyzing the response are started at the moment thatreflecting patch (21) is detected.

[0050]FIG. 2 shows a top view of a the present embodiment. Carpet (6) isfixed in clamp (5) having an opening (11). The distance between bothsides (5 a and 5 b) of clamp (5) is about 3.5 cm. Predetermined surface(6 a) of carpet (6) within clamp (5) is in a predetermined position incontrast to the part of the carpet (6 b) which is not within the clamp.Carpet (6) is moved in the direction of the arrow (24) at a speed of1000 m/hour past two NIR-spectrometers (1) having irradiation beams (20)which are continuously emitted. Reflecting patch (21, not shown) ispositioned in such a way that the moment is detected at which point A(about 1 cm from clamp side 5 a) crosses line C. At that momentmeasuring of the response is started. Thus, measuring the response isstarted while predetermine surface (6 a) is in front of the opticalspectrometers (1). Spectra are measured (range 2400 to 2510 nm) using adetector in the NIR spectrometers (1) (not shown), the measurement timebeing about 50 ms. At the moment at which the measuring of the responseis terminated, point B (about 1 cm from clamp side 5 b) crosses line C,so that the measuring is terminated while the predetermined surface isin front of the spectrometers (8).

[0051] Description of a Preferred Embodiment in which a Guide System isPresent

[0052]FIG. 3 shows transport rail (2) and one transport unit (3) in thearea of near-infrared (NIR) spectrometer (1). The arrow indicates thedirection of transport. Transport unit (3) comprises a carriage (7)which can be moved in transport rail (2) using a chain (not shown),clamp (5) (coupling means), and a body (4) which connects clamp (5) andcarriage (7). A carpet (6) is fixed to clamp (5), having opening (11)through which a part of carpet (6) can be irradiated with theirradiation beam of optical spectrometer (1). In this figure carpet (6)is in a position that it can be irradiated through opening (11) withirradiation beam (20). At its upper part, body (4) is provided with twowheels (9) (guiding members) which can cooperate with guide rail (8).The combination of two wheels (9) and guide rail (8) prevent rotationaround an axis parallel to irradiation beam (20). This improves theaccuracy of the identification. A pair of guide rails (10) (guidingelements) is also present. Body (4) can be guided between said pair ofguide rails (10). This prevents movement of the body (4) and clamp (5)in the transverse direction, which improves the accuracy of theidentification. An accurate identification can take place duringmovement of the carpet past NIR spectrometer (1). The transport systemmay for instance be provided with 50 transport units. The transport ratemay for instance be 1000 m/hour.

1. Process for identifying articles which are at least partly made from at least one polymer, using an optical spectrometer and a transport system, said process comprising the steps of: a) moving the articles past the optical spectrometer using the transport system b) irradiating the articles and measuring the response of the irradiated articles using the optical spectrometer, analyzing the response to identify the articles as to the type of polymer characterized in that the process also comprises the step of c) at least periodically irradiating an external reference object, measuring the response of the irradiated reference object using the optical spectrometer, and using the measured response for the analysis of step b).
 2. Process according to claim 1, characterized in that the response of the irradiated reference object is used for correction of background signals.
 3. Process according to claim 1, characterized in that the response of the irradiated reference object is used for correction for drift.
 4. Process according to claim 1, characterized in that the response of an irradiated reference object is used for correction of background signals and that the response of an irradiated reference object is used for correction for drift.
 5. Process according to any one of claims 1-4, characterized in that the surface material of a reference object is made from one of the polymers to be identified.
 6. Process according to claim 5, characterized in that one of the polymers to be identified is polyamide 6 and/or polyamide 6,6 and that the surface material of the reference object is made from polyamide 6 and/or polyamide 6,6.
 7. Process according to any one of claims 1-6, characterized in that the reference object is moved past the optical spectrometer.
 8. Process according to any one of claims 1-7, characterized in that the reference object is moved past the optical spectrometer using endless transporting means.
 9. Process according to any one of claims 1-9, characterized in that the reference object is moved past the optical spectrometer using the transport system.
 10. Process according to any one of claims 1-10, characterized in that the reference object is fixed to the transport system and that the fixed reference object is moved past the optical spectrometer, and irradiated.
 11. Process according to any one of claims 1-11, characterized in that the reference object and/or the articles are fixed to transport system and that the fixed reference object and/or the articles are moved past the optical spectrometer, and irradiated.
 12. Process according to any one of claims 1-12, characterized in that the transport system comprises a transport rail, that the reference object and/or articles are fixed to the transport rail and that the fixed reference object and/or the fixed articles are moved past the optical spectrometer, and irradiated.
 13. Process according to any one of claims 1-13, characterized in that the reference object and/or articles are moved past the optical spectrometer, and irradiated in a predetermined position.
 14. Process according to any one of claims 1-13, characterized in that separate detecting means are used for detecting when a reference object is in front of the optical spectrometer.
 15. Process according to claim 14, characterized in that a predetermined surface the articles and/or reference object is irradiated and that the process also comprises the step d) of determining when the predetermined surface of the articles and/or reference objects is in front of the spectrometer, and that the irradiation, measuring the response, and/or analyzing the response is started for each article and/or reference object individually, while the predetermined surface of said individual article and/or reference object is in front of the spectrometer.
 16. Process according to any one of claims 1-15, characterized in that the optical spectrometer is an infrared spectrometer.
 17. Process according to any one of claims 1-16, characterized in that at least part of the articles are at least partly made from a polyamide.
 18. Process according to any one of claims 1-18, characterized in that at least part of the articles are at least partly made from polyamide-6 and/or that at least part of the articles are at least partly made from polyamide 6,6.
 19. Process according to any one of claims 1-19, characterized in that the articles are textile articles.
 20. Process according to claim 19, characterized in that the textile articles are carpets or carpet materials.
 21. Apparatus for the process according to any one of claims 1-20, said apparatus comprising: a) an optical spectrometer (1) b) a transport system, said transport system comprising a transport rail (2) and transport units (3), the transport units comprising a body (4), coupling means (5) for fixing the articles (6) to the transport units, the transport units being movably connected to the transport rail c) a guide system (8,9) which is capable of cooperating with the body and/or coupling means, said guide system at least being present in the area of the optical spectrometer.
 22. Apparatus according to claim 20, characterized in that the guide system comprises a guiding element (8) which is essentially parallel to the transport rail, said guiding element being capable of cooperating with the body and/or coupling means.
 23. Apparatus according to claim 21, characterized in that the body and/or coupling means comprise one or more guiding members (9) which can cooperate with the guiding element.
 24. Apparatus according to claim 22, characterized in that said one or more guiding members are rotatable elements.
 25. Apparatus according to any one of claims 20 to 23, characterized the guide system comprises a pair of guiding elements (10) which are essentially parallel to the transport rail and which are capable of receiving the body and/or coupling means.
 26. Apparatus according to any one of claims 20 to 24, characterized in that the guide system is a transversal guide system.
 27. Apparatus according to any one of claims 20 to 25, characterized in that the guide system is a longitudinal guide system.
 28. Apparatus according to any one of claims 20 to 26, characterized in that the optical spectrometer is an infrared spectrometer.
 29. Apparatus according to any one of claims 20 to 27, characterized in that the coupling means have openings (11) through which an article which is coupled with said coupling means can be irradiated with an irradiation beam. 